linux-kernel - Re: Attempted summary of suspend-blockers LKML thread

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Date:	Wed, 4 Aug 2010 16:39:58 -0700 (PDT)
From:	david@...g.hm
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Arve Hjønnevåg <arve@...roid.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Arjan van de Ven <arjan@...radead.org>,
	"Ted Ts'o" <tytso@....edu>, linux-pm@...ts.linux-foundation.org,
	linux-kernel <linux-kernel@...r.kernel.org>, mjg59@...f.ucam.org,
	pavel@....cz, florian@...kler.org, stern@...land.harvard.edu,
	swetland@...gle.com, peterz@...radead.org, tglx@...utronix.de,
	alan@...rguk.ukuu.org.uk
Subject: Re: Attempted summary of suspend-blockers LKML thread

On Thu, 5 Aug 2010, Rafael J. Wysocki wrote:

> On Thursday, August 05, 2010, david@...g.hm wrote:
>> On Wed, 4 Aug 2010, Rafael J. Wysocki wrote:
>>
>>> Subject: Re: Attempted summary of suspend-blockers LKML thread
>>>
>>> On Wednesday, August 04, 2010, david@...g.hm wrote:
>>>> On Wed, 4 Aug 2010, Rafael J. Wysocki wrote:
>>>>> In the suspend case, when you have frozen all applications, you can
>>>>> sequentially disable all interrupts except for a few selected ("wakeup") ones
>>>>> in a safe way.   By disabling them, you ensure that the CPU will only be
>>>>> "revived" by a limited set of events and that allows the system to stay
>>>>> low-power for extended time intervals.
>>>>
>>>> the benifit of this will depend on what wakeups you are able to avoid by
>>>> putting the hardware to sleep. Depending on the hardware, this may be not
>>>> matter that much.
>>>
>>> That's correct, but evidently it does make a difference with the hardware
>>> Android commonly runs on.
>>
>> Ok, but is there a way to put some of this to sleep without involving a
>> full suspend?
>
> Technically, maybe, but we have no generic infrastructure in the kernel for that.
> There may be SoC-specific implementations, but nothing general enough.

well, I know that we have specific cases of this (drive spin-down, cpu 
speed, display backlight for a few examples), is it worth trying to define 
a generic way to do this sort of thing? or should it be left as a 
per-device thing (with per-device knobs to control it)

I thought I had seen discussion on how to define such a generic power 
management interface, and I thought the results had been acceptable.


David Lang
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